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Lambic: A Beer Worth the Wait

Photo by Getty Images/Fabian Krueger 

Belgium is home to an incredible diversity of beers. Among the most iconic is lambic, a sour wheat ale brewed in the Zenne Valley region near Brussels. Unlike other modern beers — outside of a few newer sour craft beers — lambic wort is intentionally inoculated with wild airborne microorganisms. The characters (aromas or flavors) these wild “bugs” leave behind are part of the signature flavor of this unique beer.

The Wild Taste of Lambic

Lambic is usually pale, but fruited versions may display the color of the fruit. Modern bottled versions are often highly carbonated. The aroma of a lambic typically exhibits a lactic sourness, often with a fruity ale note. Some examples additionally show some “funk.” Common “funky” characters are described as “barnyard” and “horse blanket.” Less commonly, there may be a “baby diaper” note. These characters — as they’re not generally considered pleasant — should be restrained. However, in some examples, they’re fairly strong. In others, they’re not detectable under the sourness of the lactic acid. The funky characteristics come from wild microorganisms that grow early in the fermentation, as well as a particular wild yeast (Brettanomyces) that grows slowly late in the fermentation. The sour character comes from strains of Lactobacillus and Pediococcus bacteria.

The flavor of lambic is sour, occasionally with some “bready” notes from the wheat. In fruited examples, the fruit character can range from almost imperceptible to moderately strong. Traditional lambics are generally dry to very dry, but some nontraditional versions imported to the U.S. are pasteurized and back-sweetened. In Belgium, some lambic drinkers add sugar to their drinks to cut through the sour flavor.

There’s no hop aroma or bitterness in a lambic. Hops are an ingredient of lambic, but they’re aged before use and don’t contribute any significant level of bitterness or aroma. They may contribute a small degree of astringency. Overall, sourness, dryness, and a little astringency give lambic a puckering mouthfeel.

All the main characters in a lambic — especially sourness, dryness, and the level of funk — can vary substantially among examples. Given that a wild fermentation occurs alongside the “normal” fermentation, and that the beer is then aged in oak barrels (which themselves are home to wild bacteria and yeasts), a wide variety of outcomes isn’t that surprising. Lambic brewers have their ways of managing fermentations, and lambics are frequently blended for some degree of consistency, but this makes the category full of truly wild beers.

Truly Belgian Production

Photo by Flickr/Allagash Brewing

Traditional lambic production includes steps not seen in the production of any other beer. A typical lambic grist is about 65 percent pale barley malt and 35 percent raw, unmalted wheat. The wheat is usually soft white wheat. The brew day begins with a turbid mash, a step mash program that involves an initial thick mash, and as it progresses, liquid is drawn from the grains and heated in the kettle, while boiling water is added to the mash to raise the temperature through a series of gradual steps. Although the mash starts thick, it ends up much thinner. After mashing, the grain bed is sparged with hot water — around 194 degrees Fahrenheit — and a large amount of wort is collected. Both the sparge water temperature and the large volume of wort collected contribute to a level of tannin extraction that’s higher than in most beers. This voluminous, low-gravity wort requires a long boil to condense; three hours or more isn’t unusual. The hopping rate is fairly high, but the bitterness imparted is low because aged hops are used in the kettle. After the boil, the wort is pumped to a wide, shallow vessel called a “coolship,” and the beer cools in this vessel overnight. During this cooling period, it’s inoculated with the local microflora in the air that flows over the coolship. The next day, the beer is then pumped to barrels used in previous lambic fermentations, where it’s further inoculated with souring bacteria from the wood.

Photo by Flickr/Allagash Brewing

Early in the fermentation, a variety of wild microorganisms grow in the wort. During this phase, some of the beer’s most off-putting funk, if it exhibits any, is developed. Soon, however, brewer’s yeast takes over, causing the alcohol content of the beer to rise and the pH to drop. This kills the vast majority of wild microorganisms. The fermentation by beer yeast ends quickly, and then the beer begins to sour. The Lactobacillus and Pediococcus begin consuming carbohydrates that the beer yeast couldn’t digest, and they produce lactic acid. It takes at least a few months for the beer to become noticeably sour, and most lambic producers let the initial fermentation go for a year. As the fermentation progresses, the wild yeast Brettanomyces begins to grow, lending the barnyard character, if that’s present in the beer. While the beer ferments, oxygen slowly penetrates the barrel over time. This tiny amount of oxygen is thought to be a good thing for the sour beer fermentation.

Photo by Flickr/Allagash Brewing

Making Lambic at Home

If you have the patience, and you’re willing to change some of your normal brewing practices, you can brew a respectable lambic-style beer at home. The key microorganisms are all available commercially. In fact, both Wyeast and White Labs sell blends of these microorganisms specifically for lambic-style beers. Traditional lambic-makers brew during the cooler months of the year, and take the hot summers off. Spring is a great time for homebrewers to begin a sour beer. The main fermentation can complete at normal ale temperatures, and then the beer can sour over the summer. During this time, the temperature of the fermenter can be allowed to rise, and the added heat will help the souring bacteria do their work more quickly.

A traditional lambic is made from barley malt and raw wheat. As a homebrewer, you can use this grist, or you can use malted barley and malted wheat. An authentic turbid mash is a hassle, but you can simplify it. For example, you can do an ordinary step infusion mash with rests at 113 degrees Fahrenheit, 131 degrees, 149 degrees, 158 degrees, and 167 degrees. The rest at 149 degrees should be the longest, around 45 minutes. Or, you can dough in to 113 degrees and slowly heat the mash to 167 degrees, with a 45-minute rest at 149 degrees. Or, you can save time and just do a single infusion mash with a 60-minute or 90-minute rest at 149 degrees.

Sparging with hot water — around 194 degrees — mimics the traditional Belgian brewing practice and gives the beer a small amount of tannic astringency, something that’s desired in a lambic.

How much wort to collect is your next decision. If you want to be more traditional, collect 7 or 8 gallons of wort, and boil it for 2 to 3 hours. Or, you can shorten your brew day by collecting about 6-1⁄2 gallons and boiling it for 90 minutes.

I use aged hops if I have them, but if not, I simply switch to a low level — less than 10 IBU — with low-alpha noble hops. Use whole hops if you can, but pellets will also work.

A coolship is something most homebrewers don’t have, and with the yeast and bacteria mixes available, there’s no reason to attempt to contaminate your wort with microorganisms from your environment. Just cool the wort as you normally do, and transfer it to a plastic bucket fermenter. Pitch the yeast and bacteria blend, and let the beer ferment. Buckets are actually more permeable to oxygen than wooded barrels are, but I’ve found that they still work fine.

With the commercial blends of microorganisms available to homebrewers these days, you can brew sour beers with a high degree of success. The most important variable is time. If you give these beers time to age, they’ll sour gradually and taste wonderful. When they’re young, they can be rough. You need at least 9 months of aging to yield a drinkable sour beer. Further aging will improve it.

If you want to add oak to your fermenters, use approximately 2 to 3 ounces of French oak cubes. Soak the cubes in water for a week or so, with a few changes of the water. The barrels lambic brewers use are rendered neutral from use and therefore don’t impart a strong oak flavor or aroma.

Fruit Lambics

Photo by Shutterstock/Haelen Haagen 

One year after brewing your lambic, you may want to add fruit to it. The two most popular fruit lambics are framboise (raspberry lambic) and kriek (cherry lambic). To make a fruited lambic, add 1⁄2 pound of raspberries per gallon or 1 pound of cherries per gallon to your base lambic. Use fresh, whole fruit that’s been washed. Cut off any bruises or blemishes. You can also use fruit purée. You don’t need to sanitize the fruit. If using cherries, remove any stems. You can pit the fruit, but it’s not necessary. Allow the beer contact with the fruit for at least three months, although 6 to 9 months is more traditional.

Bottle and carbonate for up to 5 volumes of carbon dioxide. Young lambics, or beers that have had a short contact time with the fruit, may over-carbonate. Bottle in heavy bottles, and monitor carbonation by opening a bottle occasionally. Store in a container in which a burst bottle won’t cause problems. For example, line a sturdy case box with a plastic garbage bag. Carbonate to a lesser degree, around 3 volumes of carbon dioxide, if you’re concerned about the potential for burst bottles.

Gueuze

One type of traditional lambic is gueuze. Gueuze is a blend of young and old lambics. “Young,” in this case, means 1 year old, and “old” means either 2 or 3 years old. A homebrewer can brew lambic-style ales for three years, and then blend a gueuze from 1-, 2-, and 3-year-old lambic in the fourth year. If you’re wondering who would ever do such a thing, I did. Once. (And for my efforts, I won Best of Show at the Austin ZEALOTS Homebrew Inquisition that year.)

Here’s a plan that’ll put you in position to blend a gueuze four years from now. The basic idea is to brew two buckets of lambic each year. Each following year, turn one into a fruit beer, and save the other one for your gueuze. You could brew just one bucket of lambic each year, but then it would be five years before you got to taste any lambic.

The 4-Year Plan

  • Year 1: Make 10 gallons of wort, and split that between two 5-gallon bucket fermenters. If you don’t have aged hops, use fresh hops. But purchase the hops for your second- and third-year batches and age them. Set your fermenters out of the way — but not so out of the way that you forget about them. Check on them every month or so to make sure there’s still water in the airlock.
  • Year 2: In the spring of the second year, rack one of the beers to another fermenter and save it until fruit is in season. When it is, make a kriek or framboise. Make 10 more gallons of wort, and split that between two 5-gallon buckets. For this wort, you’ll have hops that’ve aged at least 1 year.
  • Year 3: In spring, set aside another bucket to make a second fruit beer. This’ll leave you with one bucket of 1-year-old lambic and one bucket of 2-year-old lambic. Brew 10 more gallons of wort — with hops that have now aged two years — and split that between two buckets. Next year, you’ll blend the three beers together to make your gueuze.
  • Year 4: Split off another bucket to make another kriek or framboise. And then, it’s finally time to blend the gueuze.

When it comes time to blend the gueuze, traditional lambic producers have a brewery full of barrels to select from. They can sample from their barrels, select those to contribute to their gueuze, dedicate others to fruit beers, and tag others for continued aging (or the drain). You, in contrast, will have three buckets. Still, if your three beers turned out well, you can blend fine gueuze at home.

Photo by Shutterstock/Marc Venema

Blending Strategy

The best-tasting gueuze may not utilize all of your available lambic. Your beers will likely show varying degrees of sourness, funk, and residual sweetness, and you may want to tailor your blend to emphasize or de-emphasize any of these characters. If you enjoy a very dry and acidic lambic, your blend should be dominated by the 3-year-old lambic. For example, you may want to blend all 5 gallons of the 3-year-old lambic with 2-1⁄2 gallons of the 2-year-old lambic, and only a little more than 1 gallon of the young lambic. This would yield between 8-1⁄2 and 9 gallons of gueuze. The leftover lambic could be used for fruit lambics, or racked to a carboy and stored for future use in other blends.

For a mellower lambic, you may want to blend all of the 2-year-old lambic with smaller amounts of the young lambic, and enough 3-year-old lambic to hit your preferred level of acidity and funk. You can take samples and make test mixes to determine your favorite blend. Remember that the beer will continue to age in the bottle, and will be highly carbonated once it’s conditioned. When finished, the beer will be drier and more acidic than it is at the time of blending.

Blends with higher percentages of young lambic will be the least acidic and contain the most microorganisms. However, a gueuze blend should never be dominated by the young lambic. It won’t be sour enough and could result in severely overcarbonated bottles.

Post-Blend Conditioning

Once blended and bottled, the gueuze should sit for at least a few months in a warm place, optimally in the mid-70s. Better yet, let it age about a year before it’s consumed.

Gueuze is traditionally bottle-conditioned, with enough added sugar to highly carbonate the beer to 4 or 5 volumes of carbon dioxide. Given that your blend will include some young lambic, carbonation can be tricky. You can estimate the amount of unfermented carbohydrates left in the beer, based on your final gravity, but you won’t know what percentage of them will be utilized by the wild yeast and bacteria during conditioning. A realistic approach is to aim for a target level of carbonation around 3 to 3-1⁄2 volumes of carbon dioxide, but it may end up more highly carbonated than this.

Making a lambic at homes takes plenty of patience. A “plain” lambic takes a year; a fruit lambic takes two years. And making several lambics in order to blend your own gueuze takes four years. However, for fans of this unique beer, their patience is rewarded with a wonderful, complex beverage that’s unlike any other.

Want to try your hand at creating a little Belgium beer in your own home? Start with this Brussels-Style Base Lambic Beer Recipe.


Chris Colbyis a writer with a background in biology and brewing. He lives with his wife and their cats — including their new kitten with the Scandinavian name Lagertha — in Bastrop, Texas. Chris enjoys gardening and drinking beer while admiring his garden.

Published on May 18, 2020
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